1. Field of the Invention
The present invention relates to a method for fabricating a liquid crystal display device, and more particularly to a method for fabricating a pixel electrode of a liquid crystal display device (hereinafter referred to as an "LCD device").
2. Description of the Related Art
In a typical TFT (thin film transistor)-LCD device, an ITO (indium tin oxide) film is used as a transparent conductive film. A well-known method for fabricating the TFT-LCD device can be broadly classified into three processes as follows:
(1) forming a TFT array on a first glass substrate; (2) forming a color filter including R(red) filters, G(green) filters and B(blue) filters, on a second glass substrate; and (3) forming an LCD cell by adhering the two glass substrates to each other in a spaced relationship and injecting liquid crystal between them.
The TFT array forming process includes the steps of forming a gate electrode, forming a gate insulating layer, forming semiconductor and ohmic layers, forming a pixel (picture element) electrode and forming source/drain electrodes. The pixel electrode forming step comprises the steps of depositing an ITO film on a glass substrate, patterning a photoresist layer, etching back the ITO film using the patterned photoresist layer as an etching mask, and removing the patterned photoresist layer.
The method of forming a TFT-LCD pixel electrode is shown in FIGS. 1A to 1F. Referring to FIGS. 1A and 1B, on a glass substrate 1 an ITO film 2 is coated, and then a photoresist layer 3 is deposited on the ITO film 2. Next, an exposure step is performed as shown in FIG. 1C. Using a photo-mask 4, light 5 is irradiated upon the photoresist layer 3 through the photo-mask 4. As a result, a patterned photoresist layer 3' is formed on the ITO film 2, as shown in FIG. 1D.
As shown in FIG. 1E, using the patterned photoresist layer 3' as an etching mask, an etching process of the ITO film 2 is carried out. A patterned ITO film 2' is then formed after removal of the patterned photoresist layer 3', as shown in FIG. 1F. The patterned ITO film 2' formed by this method is used as a pixel electrode.
However, using the method described above, a bad pattern is frequently formed while patterning the photoresist layer. This problem arises because coating uniformity of the photoresist layer is poor due to a high friction coefficient in the ITO film serving as a pixel electrode. A good pattern for the pixel electrode is therefore difficult to obtain.